In one such known precision adjustment head (DE-GM 7 409 979), an axially displaceable positioning rod is provided in the housing, which carries an oblique toothing as the positioning member. This engages in a corresponding oblique toothing provided on the slide. However, as a result of manufacturing tolerances, play arises between the two oblique toothings, which influences the positioning accuracy of the slide. For operations requiring the highest accuracy, this known adjustment head is accordingly not suitable. In this connection it is to be noted that precision adjustment heads with automatically operable slides are required in order to be able to work programmed working diameters of various sizes, also however for automatic cutting correction. Thus, in an automatic machining, the final working diameter of work pieces can be automatically, supplementarily controlled. If the ascertained diameter measurement lies outside the predetermined tolerances, which can arise for example from cutter wear or an early raising of the cutter from the workpiece surface, then the tool must be adjustable automatically and without stopping the machine to the correct working diameter with the highest accuracy.
The invention is therefore based on the problem of providing a precision adjustment head of the above mentioned kind, for a machine tool, especially a boring machine or the like, in which the axial movement of the positioning member is converted in simple manner, without play, into a radial movement of the slide, and which is accordingly characterised by the highest working accuracy.
This is attained according to the invention in that the insert is adjustable and lockable on the positioning member, perpendicular to the groove bottom.
By means of adjustment of the insert perpendicular to the groove bottom there is obtained a play free abutment of its abutment surfaces tapering towards the groove bottom against the flank surfaces of the groove. This play-free abutment can be attained by virtue of the adjustability of the insert even with less tight manufacturing tolerances. By virtue of the complete freedom of play between the positioning member and the positioning element, the precision adjustment head has a very high working accuracy.
A particularly advantageous development of the invention consists in that the positioning element is a disc in whose front face the groove is worked, which is recessed into a recess of the slide and can be fixed in a predetermined angular position with respect to the slide. By virtue of this development it is possible to alter the transmission ratio between the positioning member and the positioning element and, in this manner, adapt the fine adjustment head to the current required working accuracy.
If for example the disc is so set that its groove is inclined at an angle of 26.degree.34' with respect to the housing axis, an axial adjustment of the positioning member of 1 mm will then move the slide by 0.5 mm and accordingly lead to an alteration of the working diameter of 1 mm.
On the other hand, if the disc is so adjusted that its groove is inclined at an angle of 2.degree.52' with respect to the housing axis, then an adjustment of the positioning member of 1 mm in the axial direction yields a radial adjustment of the slide of 0.05 mm and thereby an alteration of the working diameter of 0.1 mm.